The Hope Spinel, the 50.13 ct. octagonal-cut stone that was once part of Henry Philip Hope’s renowned gem collection, sold for an incredible $1.5 million at the Bonhams London Sept. 24 auction, breaking the record for price-per-carat for a spinel. 

The price-per-carat was $30,000, nearly double the previous price-per-carat record for a spinel—$16,000, set in 2013.

The exceptional stone is set in a 19th-century silver and gold brooch and flanked by diamonds. It last sold at auction in 1917. 

Bonhams reports that bidding wars were fierce, with bidders competing in person, online, and over the telephone. An unnamed telephone bidder won the auction. 

“We are delighted with the price it has made,” said Jean Ghika, director of jewelry for the UK and Europe for Bonhams. “It was an exceptional gemstone with a priceless provenance. These pieces just don’t come to the open market often, and when they do, they are hotly contested. Bonhams is honored to have been chosen to handle the sale of such a unique and magnificent gem.” 

The auction house had estimated the stone would sell for between $227,000 and $304,000. 

JCK